This invention relates to a method of dust-control treatment of particulate material in open top hopper cars by spraying with a fluid composition which penetrates the surface of the material to bind particles into an adhesive, protective layer, the surface penetration occurring before effectiveness of the composition is lost due to run-off over a sloping or insufficiently wetted surface.
Although applicable to other particulate materials, this invention will be described in relation to the treatment of coal to prevent dust losses due to the action of wind on rapidly moving unit trains. Canadian Patent Application No. 886,069 describes a method of coal treatment in which an aqueous composition containing at least about 2.5% of a binder material consisting of solid material in an aqueous suspension of an asphalt emulsion or a black liquor lignin product containing 0.1 to 2.0% of an appropriate wetting agent results in the formation of a crust layer which provides protection against such wind action. Rapid wetting of the coal surface due to use of the selected wetting agent makes it possible to apply about 50 gallons of treatment composition to the surface of coal in a car as the car advances at a speed of about 0.5 mile per hour. Simple, single jet spray means was used. It was observed that the use of larger quantities of binding composition resulted in the thicker crusts and more effective protection. However, with a moving train, such larger quantities had to be applied more rapidly than they could be completely absorbed into the coal bed.
The present invention provides means of spraying which ensures rapid, deep penetration of surface coal. The quantity of treatment composition which can be effectively applied to the surface of the coal as a car moves under a spray header is substantially increased.
There are many known methods of spraying liquids and coatings onto surfaces. However, these do not meet the requirements of the present situation in which the surface of coal in open top gondola cars must be wetted sufficiently in the time the car passes under the header to provide an adequately bonded protective layer. The problem of run-off of wetting composition is intensified at the ends of the cars where the coal surface slopes downwardly, particularly when spraying is done immediately after loading from a hopper under which the moving cars pass. Although delay of spraying until car motion causes settling and levelling of the coal would decrease run-off, maintenance of spraying facilities some distance from loading facilities would be more costly.
The following patents may be considered to be relevant prior art to the present invention.
U.S. Pat. No. 3,237,598 provides means for oscillating a spray nozzle header used for applying a coating composition to an article.
U.S. Pat. No. 3,282,273 relates to equipment for pneumatic spraying of a liquid onto workpieces in which a sprayhead is moved reciprocally across a spraying chamber at right angles to the direction of movement of the workpieces. The combined motions provide uniform distribution of the sprayed liquid.
A sub-soil irrigation device of U.S. Pat. No. 3,289,418 comprises a plurality of water injecting nozzles directed downwardly from a manifold, each nozzle being within a tubular body which pierces the soil. Water is discharged as each tubular body enters the soil.
The spray nozzle of U.S. Pat. No. 3,292,868 has a deflector plate extending forwardly from the nozzle.
U.S. Pat. No. 3,318,725 provides for the impregnating of wood or other porous material with a treating solution. A fine, high pressure jet of liquid forms a hole of predetermined depth in the workpiece. The liquid enters the hole and diffuses laterally into the workpiece.
In the apparatus of U.S. Pat. No. 3,351,291, a flexible deflector is mounted at the end of a nozzle to provide variable redirection and dispersion of effluent from the nozzle.
U.S. Pat. No. 3,431,889 relates to apparatus which provides downward application of fluid onto a flat moving surface. The fluid is distributed by a plurality of capillary tubes extending down from a horizontal pipe.
U.S. Pat. No. 3,591,091 provides a deflector-type spray nozzle which is attached, with a changeable orifice, to the top of a supply pipe.